Dear Ghost,
Leaving aside the various degeneracies to which the limerick form often descends (and yes, I've gone that route too at times)...a-hem...
Two much worthier writers of limericks than I, NoStar and Paul_Breslin, have weighed in on the Poems Fray, and I suggest a peek at their posts regarding meter in limericks (here, here and here). There are variations in practice with regard to meter, and so the above Web site differs in its opinion on meter from Paul and perhaps even NoStar. See the citation below:
Limericks consist of five anapaestic lines.
Lines 1, 2, and 5 of Limericks have seven to ten syllables and rhyme with one another.
Lines 3 and 4 of Limericks have five to seven syllables and also rhyme with each other.
Here's something from "ancient history" on the Poems Fray, which I saved...and the first example only illustrates "plus ca change, plus ca c'est la meme chose (the more things change, the more they stay the same)". How ironic! But as for the rest, I make no claims to poetic perfection below...just to having had fun writing the limericks. ("Splorange" is an "in-joke" among Contempo, Denny and I. A good test of how long you've been around P-Fray is whether you remember the first appearance of that joke.)
wr ()()
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WR - Fray Limericks
Subject: By invitation...
From: White_Rabbit
Date: Jun 22 2005 12:38PM
White_Rabbit has turned off the way;
He's headed to Best of the Fray.
He's like Jekyll and Hyde,
Having meekness -- or pride;
You won't always like what he'll say!
Subject: "A Limerick With 'Splorange'"
From: White_Rabbit
Date: Jun 22 2005 6:06PM
Be careful what you wish for, Contrarian and Tempo...you just might get it!
One Saturday no less than FOUR eng-
Ineers tried to rhyme the word "OR-ange".
"Well, there's ONE word I've seen,"
Said their leader, "that's keen;
But what the Sam Hill is a 'SPLOR-ange'?"
wr ()()™
(with a little help from Willard R. Espy)
Subject: Ode to the Average Fray Limerick
From: White_Rabbit
Date: Jun 22 2005 10:43PM
This has to be deliberately offbeat here and there...
The lim'ricks we write to re-LAX
Are structured as if their syn-TAX
Went through an eggbeater;
And as for their meter,
It might be improved with an AXE.
wr ()()™
(borrowing that last line from Larry Niven and Jerry Pournelle)